This invention relates to a closure cap device for a container, and, more particularly, it is concerned with such closure cap device for a volatile liquid fuel storing tank of, for example, an automobile, a motor-cycle, and so forth.
It may sometimes be experienced that, if a sealing condition between the closure cap and a fuel filling port of the fuel storing tank is incomplete, vapor of the fuel are prone to leak out of the fuel tank through the fuel filling port, particularly when the fuel storing tank is heated under the immense heat of the sun in the summer time, for example, and the vapor pressure within the tank becomes very high. This leaked-out vapor of the fuel becomes a cause for the atmospheric contamination, or the so-called "air pollution," so that it is mandatory that leakage of the fuel vapor should be prevented from occurring by making complete the sealing condition between the closure cap and the fuel filling port of the fuel storing tank.
The conventionally practised structure for the closure cap for the fuel storing vessel has been such that a piece of a rubber sealing material is interposed between the closure cap and a flange of the fuel filling port so that the sealing rubber material may be simply compressed between the closure cap and the flange of the fuel filling port by a repulsive force of a compression coil spring provided in the closure cap, which is the so-called "bayonet type" cap tightening system.
In the above-described construction of the closure cap device, the effect to be derived from the sealing rubber material depends upon the repulsive force of the compression coil spring. Therefore, if the repulsive force is made large, satisfactory sealing effect can be obtained. On the other hand, however, it has such disadvantage that the fitting and removing operations of the closure cap becomes rather difficult and troublesome.